Atomic Simulation of Deformation Behavior of Polycrystalline Co30Fe16.67Ni36.67Ti16.67 High Entropy Alloy Under Uniaxial Loading

Mechanical behavior and plastic deformation mechanism of a new type of Co(30)Fe(16.67)Ni(36.6)7Ti(16.67) high entropy alloys (HEAs) have been calculated by the molecular dynamics method. The results show that the polycrystalline Co(30)Fe(16.67)Ni(36.6)7Ti(16.67) HEA has remarkable tensile plasticity and anisotropy. When the crystallographic orientation of the grain is <001>, the plastic deformation mechanism is face-centered cubic (FCC)-> body-centered cubic (BCC) transformation and deformation twins. Grain boundary and vacancy reduce the nucleation energy of FCC -> BCC phase transition, making BCC phase nucleation easy and growing in a shear manner, eventually forming deformation twins in the BCC phase. When the crystallographic orientation of grain is <110> and <111>, the plastic deformation mechanism is stacking faults, FCC -> hexagonal-close-packed (HCP) phase transformation, and deformation twins. The motion of Shockley dislocation leads to the stacking fault, intrinsic stacking fault leads to the FCC -> HCP phase transition, extrinsic stratification fault leads to the twin deformation, and the grain refining occurs during the tension process. Temperature and strain rate also have strong effects on tensile strength and elastic modulus. These results will provide a theoretical basis for the development of the HEAs and expand their application.